Experimental Performance Evaluation of a Vapor Compression Refrigeration System Using CuO–SiO?–MnO? Nanoparticle-Enhanced R134a Refrigerant with Different Capillary Tube Diameters

Abstract

Improving the energy efficiency of vapor compression refrigeration systems (VCRS) is essential due to rising energy demand and environmental concerns associated with conventional refrigerants. This experimental study investigates the performance enhancement of a VCRS using nanoparticle-enhanced R134a refrigerant and different capillary tube diameters. Copper oxide (CuO), silicon dioxide (SiO?), and manganese dioxide (MnO?) nanoparticles were dispersed individually and in hybrid combinations within 100 g of R134a to form nano-refrigerants. Experiments were conducted using two capillary tube diameters, 0.81 mm and 1.14 mm, under controlled ambient conditions ranging from 30°C to 31.6°C. Key performance parameters such as refrigerant temperatures at various system locations, suction and discharge pressures, compressor and evaporator power consumption, and coefficient of performance (COP) were evaluated at regular time intervals. The results indicate a noticeable improvement in thermal performance with the addition of nanoparticles. For the 0.81 mm capillary tube, the COP increased from 1.50 for pure R134a to 1.80 with CuO–SiO? nano-refrigerant. In the case of the 1.14 mm capillary tube, the hybrid CuO–SiO?–MnO? nano-refrigerant achieved the highest COP of 2.04–2.21, representing a significant enhancement compared to the base refrigerant. The study demonstrates that the combined effect of optimized capillary tube diameter and hybrid nanoparticles improves heat transfer characteristics, reduces compressor power consumption, and enhances overall system efficiency. These findings highlight the potential of nanoparticle-based refrigerants as an effective approach for improving the performance of small-scale refrigeration applications.

Introduction

The text presents an experimental investigation aimed at improving the efficiency and sustainability of refrigeration systems by using nano-refrigerants and optimizing capillary tube size. Conventional refrigeration systems using HFC refrigerants such as R134a face challenges related to high energy consumption and environmental impact. To address these issues, nanoparticles and phase-change-enhancing techniques are explored to enhance heat transfer and system performance.

Nanoparticles (1–100 nm) such as copper oxide (CuO), silicon dioxide (SiO?), and manganese dioxide (MnO?) possess superior thermal properties and, when dispersed into refrigerants, form nano-refrigerants with improved thermal conductivity and heat transfer capability. The study focuses on preparing stable hybrid nano-refrigerants (CuO–SiO?–MnO?/R134a), evaluating their thermal performance, and assessing long-term stability.

Experiments were conducted using two capillary tube diameters (approximately 0.81 mm and 1.14 mm) to study the effect of flow control on system performance. Key performance parameters measured included temperatures at various system points, suction and discharge pressures, compressor and evaporator power consumption, and coefficient of performance (COP).

Results show that adding nanoparticles significantly improves system performance compared to pure R134a. For the smaller capillary tube, COP increased progressively from 1.5 (pure refrigerant) to 1.8 with hybrid nanoparticles. With the larger capillary tube, further improvements were observed, with COP rising from 1.84 (pure R134a) to over 2.0 for hybrid nano-refrigerants. The best performance was achieved using the CuO–SiO?–MnO? hybrid nano-refrigerant combined with the larger capillary tube, indicating enhanced heat absorption, reduced compressor workload, and improved overall efficiency.

Overall, the study demonstrates that hybrid nano-refrigerants, along with optimized capillary tube geometry, can substantially enhance the thermal performance and energy efficiency of refrigeration systems. However, challenges such as nanoparticle stability, cost, and long-term reliability must be addressed before large-scale commercial adoption.

Conclusion

The experiments conducted using capillary tubes of varying diameters and refrigerants enhanced with different nanoparticles provide meaningful insights into the operational performance of mini ice cream plants. The collected and analyzed data form a strong foundation for evaluating how capillary tube dimensions and nanoparticle-infused refrigerants influence energy efficiency and thermal performance. In Experiment No. 1, a 0.81 mm capillary tube was used with various nanoparticle-infused refrigerants, while Experiment No. 2 employed a 1.14 mm tube with similar refrigerant compositions. Experiment No. 2.3 incorporated a combination of CuO, SiO?, and MnO? nanoparticles. The observed Coefficient of Performance (COP) across these studies ranged between 1.48 and 2.21, indicating varying degrees of thermal efficiency, with higher COP values reflecting better performance.

References

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Copyright

Copyright © 2026 Harendra Bind, Amit Shrivastava . This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.